Python Tkinter - Passing values with a button

Question

How do I pass parameters to a function through a button?

variable = str()

def RandomFunction(variable): 
    print (variable) 

EntryBox = Entry(MainWindow, textvariable = variable).pack() 
FunctionCall = Button(MainWindow, text="Enter", command=RandomFunction(variable))

It seems like it just doesnt print anything when the button is pressed. I've searched around and it seems that using lambda can fix it and allow (variable) to be passed to the function but after experimenting with lambda variable:variable I still can't get it to work.

How about my answer? I don't think you were using lambda correctly. — anon582847382
– anon582847382, Commented Mar 28, 2014 at 21:13

atlasologist · Accepted Answer · 2014-03-28 22:29:02Z

1

The other answers here work, but like a lot of things in life, there's more than one way to do what you're trying to do.

The code in your question actually mixes a couple of methods of getting data from the Entry widget. You're using textvariable and lambda, but you only need one. It seems like lambda has been covered, so here's a quick answer about textvariable:

First, you need to make your variable of a Tkinter string type like this:

variable = StringVar()

Your entry widget is fine, it's connected to the StringVar(). Your button doesn't need lambda, though, because you don't need to pass an argument to your RandomFunction().

FunctionCall = Button(MainWindow, text='Enter', command=RandomFunction).pack()

Lastly, your function needs a little rework, because it's not taking an argument anymore, it's just going to use the .get() method on your StringVar() whenever it's called:

def RandomFunction():
    print(variable.get())

You can read more about StringVar()s here: http://effbot.org/tkinterbook/variable.htm

answered Mar 28, 2014 at 22:29

atlasologist

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6 Comments

user3091974 Over a year ago

I've also tried that method, i get the error message: Attribute error: 'str' object has no attribute 'get'.

atlasologist Over a year ago

Try removing .get() then. Sometimes some simple debugging will be required.

user3091974 Over a year ago

but then i can't access the variable within the function

atlasologist Over a year ago

How so? Is this your exact code or a facsimile? You've been given three answers that should work with the code provided, but I think there must be something up with your code if nothing is working

user3091974 Over a year ago

That was it, thank you! Had just assigned it to a string, not a StringVar.

|

user2133443 · Accepted Answer · 2014-03-28 21:05:27Z

1

You use .get() to get the contents of an Entry. From the effbot page http://effbot.org/tkinterbook/entry.htm

from Tkinter import *

master = Tk()

e = Entry(master)
e.pack()
e.focus_set()

def callback():
    print e.get()

b = Button(master, text="get", width=10, command=callback)
b.pack()

master.mainloop()

answered Mar 28, 2014 at 21:05

user2133443

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Comments

anon582847382 · Accepted Answer · 2014-03-28 22:48:06Z

1

Using lambda to create a function that calls the function with the argument is fine (as long as you do it correctly):

FunctionCall = Button(MainWindow, text="Enter", command=lambda: RandomFunction(EntryBox.get))

Python will be happy with this because the lambda doesn't take any arguments.

edited Mar 28, 2014 at 22:48

answered Mar 28, 2014 at 20:59

anon582847382

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5 Comments

user3091974 Over a year ago

I've tried that and while it doesn't give me any errors it still seems like what it is printing is blank?

anon582847382 Over a year ago

Well, of course it doesn't, nothing comes up as you didn't set your string an actual value. Set variable to something like 'Hello, world!' and see what happens.

user3091974 Over a year ago

The entry widget is what allows you to enter text, this is then assigned to the variable. I've entered text into the entry box and it still isn't printed when the button is pressed.

anon582847382 Over a year ago

That's because you never extract the data from the Entry. See edits.

user3091974 Over a year ago

How would i go about extracting the data? in previous programs it has worked without any specific way of extracting the data.

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